Specify JDK for Maven to use

Question

I am trying to build a Hudson plugin I've modified and it requires jdk1.6. This is fine, but I don't see how I can tell maven where the different jdk is. I've found few mentions on the internet but they don't seem to apply to me. Some suggest adding some config to .m2/settings.xml but I don't have a settings.xml. Plus, I don't want to use 1.6 for all maven builds.

One kink is I am using mvn in cygwin, if that matters at all. It appears I should be able to make the specification in the project pom file, but the existing pom is pretty bare.

So bottom line is, is there a way to specify a jdk for a single invocation of maven?

Solution 1

So bottom line is, is there a way to specify a jdk for a single invocation of maven?

Temporarily change the value of your JAVA_HOME environment variable.

Solution 2

Seems that maven now gives a solution here : Compiling Sources Using A Different JDK

Let's say your JAVA_HOME points to JDK7 (which will run maven processes)

Your pom.xml could be :

<build>
    <plugins>
        <!-- we want JDK 1.6 source and binary compatiblility -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.6</source>
                <target>1.6</target>
            </configuration>
        </plugin>
        <!-- ... -->
        <!-- we want sources to be processed by a specific 1.6 javac -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
            <configuration>
              <verbose>true</verbose>
              <fork>true</fork>
              <executable>${JAVA_1_6_HOME}/bin/javac</executable>
              <compilerVersion>1.3</compilerVersion>
            </configuration>
        </plugin>
    </plugins>
</build>

If your developpers just add (and customize) the following lines in their settings.xml, your pom will be platform independant :

<settings>
  [...]
  <profiles>
    [...]
    <profile>
      <id>compiler</id>
        <properties>
          <JAVA_1_4_HOME>C:\Program Files\Java\j2sdk1.4.2_09</JAVA_1_4_HOME>
          <JAVA_1_6_HOME>C:\Program Files\Java\j2sdk1.6.0_18</JAVA_1_6_HOME>
        </properties>
    </profile>
  </profiles>
  [...]
  <activeProfiles>
    <activeProfile>compiler</activeProfile>
  </activeProfiles>
</settings>

Solution 3

compile:compile has a user property that allows you to specify a path to the javac.

Note that this user property only works when fork is true which is false by default.

$ mvn -Dmaven.compiler.fork=true -Dmaven.compiler.executable=/path/to/the/javac compile

You might have to double quote the value if it contains spaces.

> mvn -Dmaven.compiler.fork=true -Dmaven.compiler.executable="C:\...\javac" compile

See also Maven custom properties precedence.

Solution 4

As u said "Plus, I don't want to use 1.6 for all maven builds."....So better I will say modify your pom file and specify which jdk version to use.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.7.0</version>
            <configuration>
                <source>1.9</source>
                <target>1.9</target>
            </configuration>
        </plugin>
    </plugins>
</build>

It will ensure that your particular project uses that version of jdk.

Solution 5

I say you setup the JAVA_HOME environment variable like Pascal is saying: In Cygwin if you use bash as your shell should be:

export JAVA_HOME=/cygdrive/c/pathtothejdk

It never harms to also prepend the java bin directory path to the PATH environment variable with:

export PATH=${JAVA_HOME}/bin:${PATH}

Also add maven-enforce-plugin to make sure the right JDK is used. This is a good practice for your pom.

<build>
 <plugins>
   <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-enforcer-plugin</artifactId>
      <executions>
        <execution>
          <id>enforce-versions</id>
          <goals>
            <goal>enforce</goal>
          </goals>
          <configuration>
            <rules>
              <requireJavaVersion>
                <version>1.6</version>
              </requireJavaVersion>
            </rules>
          </configuration>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

Please, see Maven Enforcer plugin – Usage.

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Comments

[700 Software]

IntelliJ-specific answer: stackoverflow.com/questions/25888023/…

[Devanshu Mevada]

The OP is building an hudson plugin on the command line, not under hudson (at least, this is my understanding).

[acdcjunior]

Example in windows: set JAVA_HOME="C:\Java\jdk7"

[Sergey Ushakov]

This is just the starting point, but not the solution. This is the requirement for the maven compiler plugin to compile for 1.7. And then the trick is to make maven really capable of compiling for 1.7, which is not so trivial if your current java version is different...

[Jin Kwon]

Voted up! I found I can use -Dmaven.compiler.fork=true and -Dmaven.compiler.executable=/path/to/target/javac in command line.

[Paul Gregoire]

even using those java-opts, you still must add this to the compiler plugin <executable>${maven.compiler.executable}</executable>

[Enrique San Martín]

in lubuntu: JAVA_HOME="/home/desa/programas/jdks/jdk1.6.0_45/" mvn -v

[RedYeti]

And in case anyone else forgets and spends ages wondering why they can't change it: JAVA_HOME can be set for Maven (on Mac at least) in this file: /private/etc/mavenrc - And that can use something like (note the backticks not single quotes!): export JAVA_HOME=`/usr/libexec/java_home -v 1.7.0_75`

[Christophe Roussy]

Unix: export JAVA_HOME='D:/dev/java/jdk8/jre' (works for me)

[bojingo]

This was perfect for specifying the exact version of the JDK. For example, I have a project that fails when using the initial JDK 1.8, but if using JDK 1.8.0_77, it works just fine. I had both JDKs installed, and with this solution maven told me I was using the wrong version of 1.8 until I changed my JAVA_HOME path to target the specific 1.8.0_77 folder. The other answers did not allow you to be so granular on the version.

[Gaëtan Lehmann]

@JinKwon Passing options with -D works fine, even without defining it in the compiler plugin section. This is nice for occasional use or for scripting. You should put it in a separate answer so we can vote it up!

[Dave]

I appreciate @Cerber's answer below, but in the end, this is just simpler and avoids any more subtle errors. It also mimicks the way CI servers like Jenkins essentially do it.

[Paul Verest]

That is other question stackoverflow.com/questions/16723533/…

[edwin]

This solution failed when I try to run tests in Java 8 I was getting *Unsupported major.minor version 52.0 *

[ocramot]

if I change JAVA_HOME and then I do java -version, it still prints the previous version.

[Romano]

A Maven Update might be required after adding these lines (Eclipse: Right click on the project, Maven, Update project)

[Bruce Adams]

Based on this answer I run the following before executing maven: export JAVA_HOME=`java -XshowSettings:properties -version 2>&1 | grep java.home | awk '{ print $3; }'`

[Enrico Giurin]

Setting maven.compiler properties doesn't prevent the code from using methods added in java 11. For instances String.repeat(). This when building with jdk 11. So the maven builds but I wish it would fail

[Martin]

To change JAVA_HOME for a single invocation without having to reset it, use JAVA_HOME="C:\Program Files\jdk-13.0.2" mvn --version

[Enrique S. Filiage]

I've also needed to overwrite my JAVA_HOME variable. For example (in bash shell): JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64/ mvn -Dmaven.compiler.fork=true -Dmaven.compiler.executable=/usr/lib/jvm/java-8-openjdk-amd6‌​4/bin/javac spring-boot:run

[RSharma]

Thanks for the jenv maven recommendation.

[barfoos]

Highly underrated comment, with this I was able to persistently set the JAVA_HOME version in RHEL 8

[Sumit Jha]

upvoted. exactly what I needed. Thanks mate :)

[Catherine]

How to force Maven to run itself using JDK 11 and build project using JDK 1.5 ?

[mcwayliffe]

@ocramot That's because when you run java -version your shell is looking up the location of the java program in your PATH environment variable. Maven, on the other hand, is looking up where your JRE is via the JAVA_HOME environment variable.

[MADforFUNandHappy]

Also worked perfectly on MacOS 12.4 with latest and version 11 of openjdk installed through homebrew